The invention relates to a device for use in the deposition of semiconductor material, particularly silicon, from a reaction gas, in which the semiconductor material is thermally separated and deposited upon the surface of a rod-shaped carrier constructed of semiconductor material, disposed in such reaction gas and heated, with the heating current being supplied from an alternating voltage source over a remote-controlled electronic switch whereby the heating current can be controlled over an auxiliary voltage operable to actuate the remote-controlled electronic switch.
Such general type of device is disclosed in German Offenlengungsschrift 21 33 863 (VPA 71/1112). The arrangement therein disclosed functions as a so-called phase-gating control as the alternating current supplied is interrupted at least once per oscillation, and the carrier is maintained in a voltage-free state for a period longer than that corresponding to its zero passage, i.e., until an ignition of the electronic switch, during the particular oscillation, causes the carrier to again be supplied with operating voltage.
A device such as that described is able to stabilize the temperature of the rod-shaped carrier irrespective of its decreasing current-voltage characteristic. However, as the heating current is initiated intermediate the zero passages of the heating voltage, interfering loading of the alternating voltage source occurs, i.e., the lines supplying the required energy. In accordance with the prior art, such loading may be suppressed or eliminated by means of a so-called zero switch which, as compared with a phase-gating control, closes the electronic switch only in the zero passages of the heating voltage. Zero voltage switches of this type are described, for example, in "Siemens Bauteile-Informationen" (Siemens Component Information) 10 (1972), Volume 1, pages 1 through 4, and in "Funkschau" (Radio Review) (1971), Volume 20, pages 669, 670. However, it will be appreciated that in order to maintain the temperature constant at the surface of the carrier during the deposition operation, widely differing currents and voltages become a requirement. For example, at the beginning of the deposition process (assuming a rod-shaped carrier which has already been heated up to the deposition temperature) a high voltage with relatively little current is required and subsequently a considerably greater current with a relatively low voltage is required.